Norwegian Shelf large marine ecosystem

Location of the Norwegian Shelf Large Marine Ecosystem. (Source: NOAA)

The Norwegian Shelf Large Marine Ecosystem (LME) is characterized by its Subarctic climate. It is a western boundary ecosystem situated off the west coast of Norway. The Iceland-Faroe Ridge separates the relatively warm waters of the northeast North Atlantic from the cold Arctic deep water of the Norwegian Sea. A boundary current flows along the edge of the Norwegian Shelf into the Arctic region. The cold and low salinity East Icelandic Current flows southeast towards the Norwegian Basin. Climate is the primary force driving the LME, with intensive fishing as the secondary driving force. LME book chapters and articles pertaining to this LME include Ellertsen, et al, 1990; and Blindheim and Skjoldal, 1993.

Productivity

The Norwegian Shelf LME is considered a Class I, highly productive (>300 grams of Carbon per square meter per year) ecosystem based on SeaWiFS global primary productivity estimates. Its high productivity is probably linked to the nutrient rich, cold Arctic waters that characterize this LME (see Furnes and Sundby, 1980). A temperature and salinity anomaly occurring in the northern North Atlantic during the 1960s and 1970s (see speculations as to the reason for the anomaly in Dickson et al., 1988), has probably had a triggering effect on ecological events. It has had a major impact on Norwegian spring-spawning herring, the first large stock to be affected, as discussed by Dragesund et al., 1980, and the International Council for the Exploration of the Sea (ICES).

There was a change in feeding conditions for the herring stock, which had to shift further to the northeast. For more information on the effect of environmental factors on cod recruitment variability, see Ellertsen et al, 1990. For a map of the feeding and spawning area of the blue whiting in relation to the Norwegian Sea, see Blindheim and Skjoldal, 1993, p. 191. A key species in this LME is the copepod Calanus finmarchicus, which is transported from the Norwegian Sea into the Barents Sea. For the life cycle and transport of Calanus finmarchicus from the Norwegian Sea into the Barents Sea, see Blindheim and Skjoldal, 1993, p. 192. For a map of the distribution and abundance of the copepod nauplii in 1982 and in 1984, see Ellertsen et al, 1990, p. 28. There is a need for better understanding of the climate system and its impacts on the LME.

Fish and Fisheries

The Norwegian Shelf LME has a complex fishery history with concomitant influences of ecological anomalies, high fishery mortality and early implementation of management measures. The Food and Agriculture Organization (FAO) 10-year trend shows an increase in the total catch, from 500,000 tons in 1990, to 1.8 million tons in 1999 (see FAO, 2003). The average yearly catch is 1.5 million tons. The average catch composition is dominated by three groups: herrings, sardines and anchovies (almost half the catch); pelagic fishes (14% of the catch); and cods, hakes and haddocks (32% of the catch). In the 1960s and 1970s, fishing pressure increased as a result of purse seining technology. Herrings became depleted, which eventually led to a collapse. After two decades of very low abundance, herring stock has recently recovered to a total biomass of over 10 millions tons. The stock winters in the Vestfjord, and feeds all over the Norwegian Sea in the summer. Main spawning grounds are off Møre, with smaller populations spawning off of Iceland and southern Norway.

For a map of the distribution of the Arcto-Norwegian cod, see Ellertsen et al, 1990, p. 20. The spawning areas of cod are located in the Norwegian coastal current, in coastal bays and near offshore banks (see Ellertsen et al., 1989). Temperature is an important factor affecting cod recruitment. The data strongly suggests that a high temperature is a necessary condition for the formation of a strong year-class. Capelin migrates out of the Barents Sea into the Norwegian Sea. For more information on the influence of the marine environment on fish recruitment and biomass yields, see Ellertsen et al., 1990. For detailed fish catch statistics for this LME, see data collected by the University of British Columbia Fisheries Center. The overriding goal of Norwegian fisheries management is the sustainable use of living marine resources.

Pollution and Ecosystem Health

Some water pollution issues in this LME stem from Norway’s offshore oil industry, and the risk of oil spills in Norwegian waters. Poor weather and substandard ships have caused groundings and losses. For more information about pollution control in Norway, see the Norwegian Pollution Control Authority (SFT), under Norway’s Ministry of the Environment. This agency aims to promote sustainable development.

Socio-economic Conditions

The fisheries industry is the backbone of coastal Norway’s economy. The herring fishery, for instance, is of vital socio-economic importance. Norway exports fish and fish products to more than 150 countries world-wide. The fishing industry in Norway is divided into a marine and an aquaculture sector. The former employs some 15,000 fishermen at sea, and 12,000 people working in 500 fish plants along the coast. The aquaculture industry employs some 6,000 people, with fish farms all along the North Norwegian coast.

Governance

Norway established an Exclusive Economic Zone (EEZ) in 1977. It has negotiated a series of agreements with neighboring countries, including Russia, to decide on management measures and divisions of quotas on shared fish stocks. Several national measures for the management of the Norwegian Shelf LME have been implemented in Norway. ICES, the International Council for Exploration of the Seas, an organization that formulates scientific advice to fisheries authorities in the North Atlantic region, chose Norway for its symposium on the changing states of LMEs in the North Atlantic in 1999.

Shevelev, M.S., V.V. Tereschchenko, and N.A. Yaragina. 1987. Distribution and behaviour of demersal fishes in the Barents and Norwegian Seas, and the factors influencing them. In: H. Loeng (ed.). The effect of oceanographic conditions on distribution and population dynamics of commercial fish stocks in the Barents Sea. Proceedings of the third Soviet-Norwegian Symposium, Murmansk, 26-28 May 1986. Institute of Marine Research, Bergen, Norway. 181-190.

Sundby, S. and Bratland, P. 1987. "Spatial Distribution and Production of Eggs from Northeast-Arctic Cod at the Coast of Northern Norway 1983-1985". Fisken Hav. 1: 1-58.

Disclaimer: This article contains information that was originally published by the National Oceanic and Atmospheric Administration (NOAA). Topic editors and authors for the Encyclopedia of Earth have edited its content and added new information. The use of information from the National Oceanic and Atmospheric Administration (NOAA) should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.